1. Field of the Invention
The present invention relates to improvements in drum winding machines and, more particularly, to a paper machine drum winder, or reel, which continually winds successive rolls from an on-coming supply of paper web, such as from a papermaking machine. Still more particularly, this invention relates to apparatus for measuring and controlling the nip load of a wound paper roll against the reel support drum.
2. Description of the Prior Art
A device of the general type for which the improvement is made is illustrated in U.S. Pat. No. 3,743,199 and includes a mechanism for bringing a new spool, sometimes called a core in the papermaking trade, into engagement with a horizontal driven winding drum on the reel in a papermaking machine, and moving the new spool downwardly from an initial position over the drum to a wound roll winding position where the spool is supported on rails while the paper roll wound on the spool is nipped against the support drum. A web is fed onto the spool until the wound roll is completed, whereupon a new spool is started and the process is repeated.
An important factor in the successive commercial winding of paper is to provide for a uniform roll structure. To do this, it is necessary to measure and control the nip level between the winding drum on the reel and the wound paper roll. This allows for a more uniform roll structure.
Present day designs for a reel usually do not have a means for directly measuring the nip level between the winding drum and the wound paper roll. Some reels have been designed with a load cell arrangement in the secondary arms. These secondary arms of a reel usually rotate through an arc, and load cells, which are commercially available and which are used in the secondary arms, only measure force in one plane. Due to the arcuate movement of the secondary arms, the orientation of load cells in the arms changes continuously such that they measure different forces for the same nip levels at different wound roll diameters. Therefore, the roll diameter and machine geometry must be known, along with the load cell reading, in order to calculate the nip level. Other efforts to measure nip load and control the nip load by the use of load cells have problems with the mechanical mounting of the load cells. In many instances, the load cells are damaged to the point where they do not function.
It is desirable to be able to control the nip level between the winding drum and the roll of paper at all times during the winding cycle, and to do this, it is necessary to continually and accurately measure the nip force between the drum and the roll being wound, and to control this nip force as a function of the measured parameters. Further, extraneous forces can have an effect on the measuring system, and these must be compensated for. Present available systems do not provide a reliable and efficient arrangement for measuring and controlling nip pressures in a winding machine.
Another problem encountered has to do with the effect of the weight of the spool on which the roll is started. It is necessary to establish this level as a reference point for measuring nip load when the roll is started and the initial core is being brought down from the starting position above the winding drum to the winding position where it is horizontally opposite the winding support drum. Tests have shown that it is very important to the successful winding of a roll that the initial starting paper web tension and nip force between the spool and support drum be accurately controlled.
Older reel designs did not utilize any means of relieving the spool weight from the winding drum once the turn-up of the on-coming web onto a new spool was done. The result was an initial nip load of 15 PLI, or higher. These nip levels can be detrimental to roll structure. While it is desired to have a nip in the range of 5-20 PLI, the nip due to the hooks or other core-securing apparatus in the arms can contribute an additional 10-15 PLI nip load. Recent designs have provided a means of relieving the weight of the reel spool/core, but they do not have any load sensing instruments and mechanism inside the primary arms for controlling the load according to the position of the core during the beginning of a wound roll. Due to sliding friction in the hook apparatus for supporting and securing the spool while the wound paper roll increases in diameter, the nip level could not heretofore be maintained with reasonable accuracy. Also, if the individual reel spool weight does not match the set-up parameter, then the actual nip level will be inaccurate.